Erich Neumann, The Origins and History of Consciousness (Princeton
University Press, 1954) xxii n. 7:

The Anima is the personification of all
feminine psychological tendencies within a man, the archetypal feminine
symbolism within a man's unconscious. The Animus is the personification of all masculine
psychological tendencies within a woman, the archetypal masculine symbolism
within a woman's unconscious.

The anima and animus draw their power especially from the collective
unconscious, but they are also conditioned by a person's individual
experiences. They therefore have three components:

Symbolism in Dreams and Narratives: a
peer figure of the opposite sex to the ego-bearer to whom he/she has a strong
and compelling tie or bond (often a lover, brother/sister, soul-mate). Jung
said that the animus is more likely to be personified by multiple male figures,
while the anima is frequently a single female.

Anima Projection: The unindividuated man
identifies with those personal qualities that are symbolically masculine; he
develops these potentialities and to some extent integrates their unconcious
influences into his conscious personality. However, he does not recognize
qualities that are symbolically feminine as part of his own personality but
rather projects them onto women. He will project his anima—those
particular characteristics and potentialities that are significant components
of his personal unconscious and therefore carry a special emotional
charge—onto a few women for whom he will then feel a strong and compelling
emotion (usually positive but occasionally negative). Infatuation (an instant,
powerful attraction for a woman about whom he knows little) is one of the signs
of anima projection, as is a compulsive possessiveness.

Animus Projection: The unindividuated
woman identifies with those personal qualities that are symbolically feminine;
she develops these potentialities and to some extent integrates their
unconcious influences into her conscious personality. However, she does not
recognize qualities that are symbolically masculine as part of her own
personality but rather projects them onto men. She will project her
animus—those particular characteristics and potentialities that are
significant components of her personal unconscious and therefore carry a
special emotional charge—onto a few men for whom she will then feel a
strong and compelling emotion (usually positive but occasionally negative).
Infatuation (an instant, powerful attraction for a man about whom she knows
little) is one of the signs of animus projection, as is a compulsive
possessiveness.

Anima Possession: Since the
unindividuated man has not consciously developed any of his symbolically
feminine qualities (e.g. emotion, need for relatedness), his personality is apt
to be taken over or "possessed" by these qualities at times, so that
his emotional behavior and relationships may be acted out in childish and
immature ways that are apparent to others but not to him.

Animus Possession: Since the
unindividuated woman has not consciously developed any of her symbolically
masculine qualities (e.g. logic, leadership, need for independence), her
personality is apt to be taken over or "possessed" by these qualities
at times, so that she appears opinionated, argumentative, or domineering to
others, though she will not think of herself that way. In the words of Jung,
"[J]ust as the anima of a man consists of inferior relatedness, full of
affect, so the animus of woman consists of inferior judgments, or better,
opinions." Alchemical Studies: The Secret of the Golden Flower (CW
13, par.60).

Anima/Animus Integration: We can avoid
anima/animus possession and withdraw projections by integrating the
contrasexual archetype into consciousness, realizing we are cutting off our
human potential by recognizing and developing only those symbolic qualities
that match the sex of our bodies. In the words of Demaris Wehr, the anima leads
a man "into unexplored depths of feeling, relationship, and sensitivity. .
. . the integrated animus leads a woman into the world of the spirit,
erudition, and the power of the word" (66-67). Integration of the
Anima/Animus is often termed Androgyny. It
is symbolized in narratives through achievement of a special bond (frequently
sexual union/marriage) between the ego-bearer and the anima/animus figure.